Premium SKU (#30396)

* Added premium SKU

* removed duplicate enterprise license check functions

* Added license check on API layer

* lint fix

* lint fix

* refactured signature:

* test: Add comprehensive tests for license tier check functions

* fixed test

* text update

* optimised license checks

* fixedf test

* Updated license valid function

* webapp license checks

* handling prekium SKU in webappp:

* added plugin api method and general refactoring

* Updated tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/post.go

@@ -1083,11 +1083,11 @@ func unpinPost(c *Context, w http.ResponseWriter, _ *http.Request) {
 
 func acknowledgePost(c *Context, w http.ResponseWriter, r *http.Request) {
 	// license check
-	permissionErr := minimumProfessionalLicense(c)
-	if permissionErr != nil {
-		c.Err = permissionErr
+	if !model.MinimumProfessionalLicense(c.App.Srv().License()) {
+		c.Err = model.NewAppError("", model.NoTranslation, nil, "feature is not available for the current license", http.StatusNotImplemented)
 		return
 	}
+
 	c.RequirePostId().RequireUserId()
 	if c.Err != nil {
 		return
@@ -1122,11 +1122,11 @@ func acknowledgePost(c *Context, w http.ResponseWriter, r *http.Request) {
 
 func unacknowledgePost(c *Context, w http.ResponseWriter, r *http.Request) {
 	// license check
-	permissionErr := minimumProfessionalLicense(c)
-	if permissionErr != nil {
-		c.Err = permissionErr
+	if !model.MinimumProfessionalLicense(c.App.Srv().License()) {
+		c.Err = model.NewAppError("", "license_error.feature_unavailable", nil, "feature is not available for the current license", http.StatusNotImplemented)
 		return
 	}
+
 	c.RequirePostId().RequireUserId()
 	if c.Err != nil {
 		return